Some animals do not grow old with age – Isn’t that great!

Immortality is a pipeline dream cherished by each one of us. Who doesn’t want to be healthy, active and youthful for centuries together and enjoy the bliss of this beautiful world around? But unfortunately, aging is an inevitable process marked by progressive deterioration of physiological function with advancing age. Ageing is associated with increase in mortality and decline in fecundity, that is, the ability to reproduce. According to the German biologist August Weissmann, ageing is a normal process of natural selection which selects against the old and deteriorated organisms. This favors the evolution of the death mechanism so that a space is created for the next generation. This ensures the survival of the species as survival of the youthful, reproductively prolific individuals is favored.

Some age related problems observed in human beings include, loss of strength and endurance, loss of memory power, loss of bone mass and increase in the wear and tear of bones and joints, weakening of senses particularly eye sight, etc. The onset and process of aging depends largely on the genetic constitution and nutrition. However, in human beings factors like lifestyle habits and medical care also determine the aging process.

A recent study published in the journal Nature, challenges the role of evolution in leading to senescence. The aging strategies have been found to be very different during this study in some animals. These animals do not deteriorate or become infertile with age. The process of aging does not increase the chances of death in these animals. Owen Jones, a famous biologist from University of Southern Denmark in Odense compared the demographic patterns of 46 species including 11 mammals, 12 other vertebrates, 10 invertebrates, 12 vascular plants and a green alga to suggest that aging strategies are diversified amongst these species.

No association between the lifespan of the species and their degree of senescence was detected. Out of the 46 species tested, 24 species showed abrupt increase in mortality with age. Amongst these species 13 species had relatively shorter life spans and the remaining had relatively longer life spans. Guppies (Poecilia reticulata) and water fleas (an order of crustaceans) have shorter life span (days-weeks) and their mortality increases with age as seen in animals with a longer life span, for example, human beings.

When the organisms were clustered based upon their senescence patterns, mammals together formed one cluster at one end and showed an abrupt shift in mortality with age, whereas plants were clustered separately as they showed relatively lesser tendency of increase in mortality. Other organisms such as birds and invertebrates were scattered throughout. Organisms such as hermit crab, the red abalone and the hydra, a microscopic freshwater animal, which lie scattered between mammals and plants enjoy constant levels of fertility and mortality through out their life span which is for centuries together

This study helps us to understand that patterns of ageing are quite diverse amongst various organisms. The study of genes which work against the increase in mortality or deterioration might help to extrapolate the results to the human studies so that the fast deterioration associated with ageing can be controlled in some people. A different study has shown that Sirtuin family of proteins play a vital role in extending the life span of mammals. Similar studies can offer a potential solution to many age related disorders.

Also, we live with the belief that our body grows weaker with age. Studies like these question that belief and change our perspective to life.

Jones, R, O,., et al. (2013). Diversity of ageing across the tree of life. Nature. doi: 10.1038/nature12789